In the manufacture of printed circuit boards, printed circuit elements and like goods, and in processes connected with the same, it has become commonplace to deliver the articles, such as printed circuit boards, printed circuit film or the like, through a chamber in a continuous manner, while the articles are being treated by the spray of a suitable treatment fluid, such as an etchant, onto them. Often the etchant is of a corrosive nature, but on other occasions it can be various chemical solutions or even ordinary rinsing liquid, such as water. See, for example, U.S. Pat. No. 4,233,106, the disclosure of which is herein incorporated by reference.
Especially in instances when the treatment fluids are liquids that are corrosive in nature, it is undesirable to have the liquids pass outwardly of the treatment chamber, because if they did, they would require earlier replenishment than would be desirable, or would require special handling of the treatment liquid that passes outwardly of the chamber. Even further, considerations of costs are involved, in connection with loss of treatment fluid.
In the course of preventing the passage of treatment fluid outwardly of treatment chambers, it has become commonplace to locate a pair of opposed rollers, at least near the exit of the treatment chamber, although in many instances opposed pairs of rollers are located at both the inlet and exit of the treatment chamber, preventing the undesirable passage of treatment liquid out an associated opening of the chamber. In even other instances, opposed roller pairs are provided at various locations throughout the treatment chamber, not related to an opening.
In any event, opposed roller pairs are utilized in treatment chambers to prevent passage of liquid out openings, or to provide a driving means for driving the articles that are treated along their predetermined path through the chamber, generally from inlet to exit, or to both drive the articles and prevent liquid passage.
In the course of known processes, it has been commonplace for rollers to provide a nip between them for squeezing the articles as they pass through the nip, to facilitate removal of the treatment liquid from surfaces of the articles as they pass through the nip. Such rollers are generally referred to as anti-dragout rollers, because they cooperate to prevent the dragging-out of treatment liquid from the chamber at the exit end.
It will be understood that similar, although perhaps less pronounced problems can exist at the inlet end of the chamber, so that similar rollers are often used thereat.
With increased miniaturization in many industries, including the electronics industry, printed circuit articles have become thinner, lending themselves to multi-layer construction. In fact, in many instances printed circuit boards, particularly those of multi-layer types, have many layers and have thus become substantially thicker than boards as used in the past. Increased thickness also accurs with other thick articles treated with other treatment fluids, not involved with the printed circuit industry.
As articles being treated become increasingly thicker, upon their passing through a nip of opposed rollers, the nip needs to adjust to permit the articles therethrough. In the past, the upper roller of a nip pair of rollers would have its shaft slot-mounted at its ends, allowing the upper roller, by its weight, to press on the upper surface of a board being treated, while the upper roller moved upwardly, as guided by roller shaft ends sliding upwardly in slotted holes in sidewalls of the equipment. But, because the rollers are generally driven to press against the article surfaces preferably while driving the articles longitudinally of the apparatus, the limit of upward movement of a roller being lifted was determined by whatever looseness or "play" existed in the drive for the roller, or else the roller was lifted so much that its driven end became disengaged from its drive, thereby sometimes interrupting the continuous operation of a continuous process.
The present invention is directed toward effecting the treatment of articles as described above, in such a way that as articles pass through the nip of an opposed pair of rollers, they cause one of the rollers to move away (preferably an upper roller moving upwardly) from the path of travel of articles being treated, in separation of the roller nip, while that moved roller remains driven, even when an article being treated is of substantial thickness. When the articles passes the nip, the roller returns automatically to its opposed roller to close the nip, all the while being driven.